Tena koe Justin Try aggregate(): e.g.,
aggregate(myframe[,4], myframe[,1:3], min) HTH .... Peter Alspach > -----Original Message----- > From: r-help-boun...@r-project.org > [mailto:r-help-boun...@r-project.org] On Behalf Of JustinNabble > Sent: Tuesday, 12 January 2010 1:58 p.m. > To: r-help@r-project.org > Subject: [R] How to get minimum value by group > > > I'd like to get a long data set of minimum values from groups > in another data set. > The following almost does what I want. (Note, I'm using the > word factor differently from it's meaning in R; bad choice of words) > > myframe = data.frame(factor1 = rep(1:2,each=8), factor2 = > rep(c("a","b"),each=4, times=2), factor3 = > rep(c("x","y"),each=2, times=4), > y=1:16) > attach(myframe) > minimums = by(y, list(factor1, factor2,factor3), min) > detach(myframe) > > The problem is that "minimums" is object of class "by", which > looks like some kind of array with the number of dimension > equal to the number of factors. I just want two dimensions > though, with factors in columns. I can't figure out how to > reformat it to something like this: > > factor1 factor2 factor2 y > 1 a x 1 > 2 a x 9 > 1 b x 5 > ... > > I could make nested for loops, but I'd like something that > will work for an arbitrary number of factors. I've seen some > functions that will rearrange data (e.g. reshape), but they > all seem to require a data.frame to start with. > -- > View this message in context: > http://n4.nabble.com/How-to-get-minimum-value-by-group-tp10117 > 45p1011745.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
